The present invention relates generally to an apparatus for feedback control of the ratio of air to fuel of the air-fuel mixture supplied to an internal combustion engine, and particularly to an apparatus for the above-mentioned feedback control which senses low temperature of the engine to supply a rich air-fuel mixture to the engine in order to ensure cold engine start.
Various apparatuses have been proposed to supply an optimum air-fuel ratio of the air-fuel mixture to an internal combustion engine for reduction of noxious components contained in exhaust gases, one of which is an apparatus using the concept of feedback control of the air-fuel ratio of the air-fuel mixture. The apparatus generally comprises a sensor, such as an oxygen analyzer, for sensing a component of the exhaust gases and generating an electrical signal representative thereof, a differential signal generator being connected to the sensor for generating an electrical signal representative of the differential value between the signal from the sensor and a reference signal, and control circuit connected to the differential signal generator for controlling an actuator such as an electromagnetic valve, which is attached, for example, to a fuel supply conduit of a carburetor, in response to the differential value therefrom to regulate the mass ratio of air to fuel.